Along with surgery and radiotherapy, chemotherapy continues to be an effective therapy for many cancers. In fact, several types of cancer, such as Hodgkin""s disease, large cell lymphoma, acute lymphocytic leukemia, testicular cancer and early stage breast cancer, are now considered to be curable by chemotherapy. Other cancers, such as ovarian cancer, small cell lung and advanced breast cancer, while not yet curable, are exhibiting positive response to combination chemotherapy.
One of the most important unsolved problems in cancer treatment is drug resistance. After selection for resistance to a single cytotoxic drug, cells may become cross-resistant to a whole range of drugs with different structures and cellular targets, e.g., alkylating agents, antimetabolites, hormones, platinum-containing drugs, and natural products. This phenomenon is known as multidrug resistance (MDR). In some types of cells this resistance is inherent, while in others, such as small cell lung cancer, it is usually acquired. Such resistance is known to be multifactorial and is conferred by at least two proteins: the 170 kDa P-glycoprotein (MDR1) and the more recently identified 190 kDa multidrug resistance protein (MRP1). Although both MDR1 and MRP1 belong to the ATP-binding cassette superfamily of transport proteins, they are structurally very different molecules and share less than 15% amino acid homology.
Despite the structural divergence between the two proteins, by 1994 there were no known consistent differences in the resistance patterns of MDR1 and MRP1 cell lines. However, the association, or lack thereof, of MRP1 and resistance to particular oncolytics is known. See Cole, et. al., xe2x80x9cPharmacological Characterization of Multidrug Resistant MRP-transfected Human Tumor Cellsxe2x80x9d, Cancer Research, 54:5902-5910, 1994. Doxorubicin, daunorubicin, epirubicin, vincristine, and etoposide are substrates of MRP1, i.e., MRP1 can bind to these oncolytics and redistribute them away from their site of action, the nucleus, and out of the cell. Id. and Marquardt, D., and Center, M.S., Cancer Research, 52:3157, 1992.
Doxorubicin, daunorubicin, and epirubicin are members of the anthracycline class of oncolytics. They are isolates of various strains of Streptomyces and act by inhibiting nucleic acid synthesis. These agents are useful in treating neoplasms of the bone, ovaries, bladder, thyroid, and especially the breast. They are also useful in the treatment of acute lymphoblastic and myeloblastic leukemia, Wilm""s tumor, neuroblastoma, soft tissue sarcoma, Hodgkin""s and non-Hodgkin""s lymphomas, and bronchogenic carcinoma.
Vincristine, a member of the vinca alkaloid class of oncolytics, is an isolate of a common flowering herb, the periwinkle plant (Vinca rosea Linn). The mechanism of action of vincristine is still under investigation but has been related to the inhibition of microtubule formation in the mitotic spindle. Vincristine is useful in the treatment of acute leukemia, Hodgkin""s disease, non-Hodgkin""s malignant lymphomas, rhabdomyosarcoma, neuroblastoma, and Wilm""s tumor.
Etoposide, a member of the epipodophyllotoxin class of oncolytics, is a semisynthetic derivative of podophyllotoxin. Etoposide acts as a topoisomerase inhibitor and is useful in the therapy of neoplasms of the testis, and lung.
Additionally, PCT publications WO 99/51236, WO 99/51228, and WO 99/51227 disclose certain compounds known to be inhibitors of MRP1.
It is presently unknown what determines whether a cell line will acquire resistance via a MDR1 or MRP1 mechanism. Due to the tissue specificity of these transporters and/or in the case where one mechanism predominates or is exclusive, it would be useful to have a selective inhibitor of that one over the other. Furthermore, when administering a drug or drugs that are substrates of either protein, it would be particularly advantageous to coadminister an agent that is a selective inhibitor of that protein. It is, therefore, desirable to provide compounds that are selective inhibitors of MDR1 or MRP1.
The present invention relates to a compound of formula I: 
where:
E is a bond or xe2x80x94C(R4)(R4)xe2x80x94;
R1 is independently at each occurrence hydrogen or C1-C6 alkyl;
R2 is independently at each occurrence hydrogen or C1-C6 alkyl;
R3 is independenty at each occurrence hydrogen, C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted (C1-C4 alkyl) C3-C8 cycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, optionally substituted (C1-C4 alkyl)-heterocycle, optionally substituted heterocycle, C1-C6 alkoxy, optionally substituted Oxe2x80x94(C3-C8 cycloalkyl), optionally substituted (C1-C4 alkoxy) C3-C8 cycloalkyl, optionally substituted (C1-C4 alkoxy)-aryl, optionally substituted O-aryl, optionally substituted (C1-C4 alkoxy)-heterocycle, or optionally substituted O-heterocycle;
R4 is independently at each occurrence hydrogen or C1-C6 alkyl;
R5 is independently at each occurrence hydrogen or C1-C6 alkyl;
or a pharmaceutical salt thereof.
The present invention further relates to a method of inhibiting MRP1 in a mammal which comprises administering to a mammal in need thereof an effective amount of a compound of formula I.
In another embodiment, the present invention relates to a method of inhibiting a resistant neoplasm, or a neoplasm susceptible to resistance in a mammal which comprises administering to a mammal in need thereof an effective amount of a compound of formula I in combination with an effective amount of an oncolytic agent.
The present invention also relates to a pharmaceutical formulation comprising a compound of formula I in combination with one or more oncolytics, pharmaceutical carriers, diluents, or excipients therefor.
Additionally, the present invention relates to a pharmaceutical formulation comprising a compound of formula I.
The current invention concerns the discovery that compounds of formula I are selective inhibitors of multidrug resistant protein (MRP1), and are thus useful in treating MRP1 conferred multidrug resistance (MDR) in a resistant neoplasm and a neoplasm susceptible to resistance.
The terms xe2x80x9cinhibitxe2x80x9d as it relates to MRP1 and xe2x80x9cinhibiting MRP1xe2x80x9d refer to prohibiting, alleviating, ameliorating, halting, restraining, slowing or reversing the progression of, or reducing MRP1""s ability to redistribute an oncolytic away from the oncolytic""s site of action, most often the neoplasm""s nucleus, and out of the cell.
As used herein, the term xe2x80x9ceffective amount of a compound of formula Ixe2x80x9d refers to an amount of a compound of the present invention which is capable of inhibiting MRP1. The term xe2x80x9ceffective amount of an oncolytic agentxe2x80x9d refers to an amount of oncolytic agent capable of inhibiting a neoplasm, resistant or otherwise.
The term xe2x80x9cinhibiting a resistant neoplasm, or a neoplasm susceptible to resistancexe2x80x9d refers to prohibiting, halting, restraining, slowing or reversing the progression of, reducing the growth of, or killing resistant neoplasms and/or neoplasms susceptible to resistance.
The term xe2x80x9cresistant neoplasmxe2x80x9d refers to a neoplasm, which is resistant to chemotherapy where that resistance is conferred in part, or in total, by MRP1. Such neoplasms include, but are not limited to, neoplasms of the bladder, bone, breast, lung(small-cell), testis, and thyroid and also includes more particular types of cancer such as, but not limited to, acute lymphoblastic and myeloblastic leukemia, Wilm""s tumor, neuroblastoma, soft tissue sarcoma, Hodgkin""s and non-Hodgkin""s lymphomas, and bronchogenic carcinoma.
A neoplasm, which is xe2x80x9csusceptible to resistancexe2x80x9d, is a neoplasm where resistance is not inherent nor currently present but can be conferred by MRP1 after chemotherapy begins. Thus, the methods of this invention encompass a prophylactic and therapeutic administration of a compound of formula I.
The term xe2x80x9cchemotherapyxe2x80x9d refers to the use of one or more oncolytic agents where at least one oncolytic agent is a substrate of MRP1. A xe2x80x9csubstrate of MRP1xe2x80x9d is an oncolytic that binds to MRP1 and is redistributed away from the oncolytics site of action (the nucleus of the neoplasm) and out of the cell, thus, rendering the therapy less effective. Preferred oncolytic agents are doxorubicin, daunorubicin, epirubicin, vincristine, and etoposide.
The terms xe2x80x9ctreatxe2x80x9d or xe2x80x9ctreatingxe2x80x9d bear their usual meaning which includes preventing, prohibiting, alleviating, ameliorating, halting, restraining, slowing or reversing the progression, or reducing the severity of MRP1 derived drug resistance in a multidrug resistant tumor.
In the general formulae of the present document, the general chemical terms have their usual meanings. For example, the term xe2x80x9cC1-C4 alkylxe2x80x9d refers to methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, cyclobutyl, s-butyl, and t-butyl. The term xe2x80x9cC1-C6 alkylxe2x80x9d refers to a monovalent, straight or branched saturated hydrocarbon containing from 1 to 6 carbon atoms. Additionally, the term xe2x80x9cC1-C6 alkylxe2x80x9d includes C1-C4 alkyl groups and C3-C6 cycloalkyls. The term xe2x80x9cC1-C6 alkylxe2x80x9d includes, but is not limited to, cyclopentyl, pentyl, hexyl, cyclohexyl, and the like. The term xe2x80x9cC3-C8 cycloalkylxe2x80x9d refers to cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. The term xe2x80x9cC5-C7 cycloalkylxe2x80x9d refers to cyclopentyl, cyclohexyl, and cycloheptyl. The term xe2x80x9cC6-C10 bicycloalkylxe2x80x9d refers to bicyclo-[2.1.1]hexanyl, [2.2.1]heptanyl, [3.2.1]octanyl, [2.2.2]octanyl, [3.2.2]nonanyl, [3.3.1]nonanyl, [3.3.2]decanyl, and [4.3.1]decanyl ring systems.
The terms xe2x80x9cC1-C4 alkoxyxe2x80x9d and xe2x80x9cC1-C6 alkoxyxe2x80x9d refer to moieties of the formula Oxe2x80x94(C1-C4 alkyl) and Oxe2x80x94(C1-C6 alkyl) respectively.
The term xe2x80x9coptionally substituted C3-C8 cycloalkylxe2x80x9d refers to a C3-C8 cycloalkyl unsubstituted or substituted once with a phenyl, substituted phenyl, or CO2R1 group.
The terms xe2x80x9coptionally substituted (C1-C4 alkyl)-(C3-C8 cycloalkyl)xe2x80x9d refers to optionally substituted C3-C8 cycloalkyl linked through a C1-C4 alkyl, optionally substituted with halo or hydroxy.
The term xe2x80x9coptionally substituted C6-C10 bicycloalkylxe2x80x9d refers to a C6-C10 bicycloalkyl unsubstituted or substituted once with a phenyl, substituted phenyl, or CO2R1 group.
The term xe2x80x9chaloxe2x80x9d or xe2x80x9chalidexe2x80x9d refers to fluoro, chloro, bromo, and iodo.
The term xe2x80x9carylxe2x80x9d refers to phenyl and naphthyl.
The terms xe2x80x9coptionally substituted arylxe2x80x9d refers to a phenyl and naphthyl group respectively optionally substituted from 1 to 5 times independently with C1-C6 alkyl, C1-C4 alkoxy, halo, hydroxy, trifluoromethyl, NR4R5, SO2NR4R5, MHxe2x80x94Pg, C1-C6 alkoxy, benzyloxy, C(O)R4, C5-C7 cycloalkyl, trifluoromethoxy, SR1, cyano, or nitro.
The terms xe2x80x9coptionally substituted (C1-C4 alkyl)arylxe2x80x9d refers to optionally substituted aryl linked through a C1-C4 alkyl, optionally substituted with halo, trifluoromethyl, or hydroxy.
The term xe2x80x9cheterocyclexe2x80x9d is taken to mean stable unsaturated and saturated 3 to 6 membered rings containing from 1 to 4 heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur, said rings being optionally benzofused. All of these rings may be substituted with up to three substituents independently selected from the group consisting of halo, C1-C4 alkoxy, C1-C4 alkyl, cyano, nitro, hydroxy, xe2x80x94S(O)mxe2x80x94(C1-C4 alkyl) and xe2x80x94S(O)m-phenyl where m is 0, 1 or 2. Saturated rings include, for example, pyrrolidinyl, piperidinyl, piperazinyl, tetrahydrofuryl, oxazolidinyl, morpholino, dioxanyl, pyranyl, and the like. Benzofused saturated rings include indolinyl, 1,2,3,4-tetrahydroquinolinyl, 1,2,3,4-tetrahydroisoquinolinyl and the like. Unsaturated rings include furyl, thienyl, pyridinyl, pyrrolyl, N-methylpyrrolyl, oxazolyl, isoxazolyl, pyrazolyl, imidazolyl, triazolyl, oxadiazolyl, thiadiazolyl, thiazolyl, pyrimidinyl, pyrazinyl, pyridazinyl, and the like. Benzofused unsaturated rings include isoquinolinyl, benzoxazolyl, benzthiazolyl, quinolinyl, benzofuranyl, thionaphthyl, indolyl and the like.
The term xe2x80x9csubstituted heterocyclexe2x80x9d refers to a heterocyclic ring substituted 1 or 3 times independently with a C1-C6 alkyl, halo, benzyl, phenyl, trifluoromethyl. Saturated heterocyclic rings may be additionally substituted 1 or 2 times with an oxo group, however, total substitution of the saturated heterocyclic ring may not exceed two substituents.
The terms xe2x80x9coptionally substituted (C1-C4 alkyl)-heterocyclexe2x80x9d refers to optionally substituted heterocycle linked through a C1-C4 alkyl, optionally substituted with halo or hydroxy.
The term xe2x80x9camino acid esterxe2x80x9d as used in this specification refers to an amino acid where the carboxy group is substituted with a C1-C6 alkyl or benzyl group. That is, the alkyl group when taken together with the carboxy group forms a C1-C6 alkyl ester. A skilled artisan would appreciate that some amino acids have two carboxy groups that may be substituted with a C1-C6 alkyl group, for example, aspartic acid and glutamic acid. This invention contemplates the possibility of amino acid mono- or diesters in these circumstances.
The term xe2x80x9cprotecting groupxe2x80x9d (Pg) refers to an amino protecting group or a hydroxy protecting group. The species of protecting group will be evident from whether the xe2x80x9cPgxe2x80x9d group is attached to a nitrogen atom (amino protecting group) or attached to an oxygen atom (hydroxy protecting group).
The term xe2x80x9camino protecting groupxe2x80x9d as used in this specification refers to a substituent(s) of the amino group commonly employed to block or protect the amino functionality while reacting other functional groups on the compound. Examples of such amino-protecting groups include the formyl group, the trityl group, the phthalimido group, the acetyl group, the trichloroacetyl group, the chloroacetyl, bromoacetyl, and iodoacetyl groups, urethane-type blocking groups such as benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl (xe2x80x9cPMOCxe2x80x9d), and the like; and like amino protecting groups. The species of amino protecting group employed is not critical so long as the derivatized amino group is stable to the condition of subsequent reaction(s) on other positions of the molecule and can be removed at the appropriate point without disrupting the remainder of the molecule. Similar amino protecting groups used in the cephalosporin, penicillin, and peptide arts are also embraced by the above terms. Further examples of groups referred to by the above terms are described by T. W. Greene, xe2x80x9cProtective Groups in Organic Synthesisxe2x80x9d, John Wiley and Sons, New York, N.Y., 1991, Chapter 7 hereafter referred to as xe2x80x9cGreenexe2x80x9d. A preferred amino protecting group is t-butyloxycarbonyl.
The term xe2x80x9chydroxy protecting groupxe2x80x9d denotes a group understood by one skilled in the organic chemical arts of the type described in Chapter 2 of Greene. Representative hydroxy protecting groups include, for example, ether groups including methyl and substituted methyl ether groups such as methyl ether, methoxymethyl ether, methylthiomethyl ether, tert-buylthiomethyl ether, (phenyldimethylsilyl)methoxy-methyl ether, benzyloxymethyl ether, p-methoxybenzyloxy-methyl ether, and tert-butoxymethyl ether; substituted ethyl ether groups such as ethoxyethyl ether, 1-(2-chloroethoxy)ethyl ether, 2,2,2-trichloroethoxymethyl ether, and 2-(trimethylsilyl)ethyl ether; isopropyl ether groups; phenyl and substituted phenyl ether groups such as phenyl ether, p-chlorophenyl ether, p-methoxyphenyl ether, and 2,4-dinitrophenyl ether, benzyl and substituted benzyl ether groups such as benzyl ether, p-methoxybenzyl ether, o-nitrobenzyl ether, and 2,6-dichlorobenzyl ether, and alkylsilyl ether groups such as trimethyl- triethyl- and triisopropylsilyl ethers, mixed alkylsilyl ether groups such as dimethylisopropylsilyl ether, and diethylisopropylsilyl ether; and ester protecting groups such as formate ester, benzylformate ester, mono-, di-, and trichloroacetate esters, phenoxyacetate ester, and p-chlorophenoxyacetate and the like. The species of hydroxy protecting group employed is not critical so long as the derivatized hydroxy group is stable to the conditions of subsequent reaction(s) on other positions of the intermediate molecule and can be selectively removed at the appropriate point without disrupting the remainder of the molecule including any other hydroxy protecting group(s).
The term xe2x80x9ccarbonyl activating groupxe2x80x9d refers to a substituent of a carbonyl that increases the susceptibility of that carbonyl to nucleophilic addition. Such groups include, but are not limited to, alkoxy, aryloxy, nitrogen containing unsaturated heterocycles, or amino groups such as oxybenzotriazole, imidazolyl, nitrophenoxy, pentachloro-phenoxy, N-oxysuccinimide, N,Nxe2x80x2-dicyclohexylisoure-O-yl, N-hydroxy-N-methoxyamino, and the like; acetates, formates, sulfonates such as methanesulfonate, ethanesulfonate, benzenesulfonate, or p-toluenylsulfonate, and the like; and halides especially chloride, bromide, or iodide.
The term xe2x80x9ccarbonyl activating reagentxe2x80x9d refers to a reagent that converts the carbonyl of a carboxylic acid group to one that is more prone to nucleophilic addition and includes, but is not limited to, such reagents as those found in xe2x80x9cThe Peptidesxe2x80x9d, Gross and Meienhofer, Eds., Academic Press (1979), Ch. 2 and M. Bodanszky, xe2x80x9cPrinciples of Peptide Synthesisxe2x80x9d, 2nd Ed., Springer-Verlag Berlin Heidelberg, 1993, hereafter referred to as xe2x80x9cThe Peptidesxe2x80x9d and xe2x80x9cPeptide Synthesisxe2x80x9d respectively. Specifically, carbonyl activating reagents include thionyl bromide, thionyl chloride, oxalyl chloride, and the like; alcohols such as nitrophenol, pentachlorophenol, and the like; amines such as N-hydroxy-N-methoxyamine and the like; acid halides such as acetic, formic, methanesulfonic, ethanesulfonic, benzenesulfonic, or p-tolylsulfonic acid halide, and the like; and compounds such as 1,1xe2x80x2-carbonyldiimidazole, benzotriazole, imidazole, N-hydroxysuccinimide, dicyclohexylcarbodiimide, and the like.
In general, the term xe2x80x9cpharmaceuticalxe2x80x9d when used as an adjective means substantially non-toxic to living organisms. For example, the term xe2x80x9cpharmaceutical saltxe2x80x9d as used herein, refers to salts of the compounds of formula I which are substantially non-toxic to living organisms. See, e.g., Berge, S. M, Bighley, L. D., and Monkhouse, D. C., xe2x80x9cPharmaceutical Saltsxe2x80x9d, J. Pharm. Sci., 66:1, 1977. Typical pharmaceutical salts include those salts prepared by reaction of the compounds of formula I with an inorganic or organic acid or base. Such salts are known as acid addition or base addition salts respectively. These pharmaceutical salts frequently have enhanced solubility characteristics compared to the compound from which they are derived, and thus are often more amenable to formulation as liquids or emulsions.
The term xe2x80x9cacid addition saltxe2x80x9d refers to a salt of a compound of formula I prepared by reaction of a compound of formula I with a mineral or organic acid. For exemplification of pharmaceutical acid addition salts see, e.g., Berge, S. M, Bighley, L. D., and Monkhouse, D. C., J. Pharm. Sci., 66:1, 1977. Since compounds of this invention can be basic in nature, they accordingly react with any of a number of inorganic and organic acids to form pharmaceutical acid addition salts.
The pharmaceutical acid addition salts of the invention are typically formed by reacting the compound of formula I with an equimolar or excess amount of acid. The reactants are generally combined in a mutual solvent such as diethylether, tetrahydrofuran, methanol, ethanol, isopropanol, benzene, and the like. The salts normally precipitate out of solution within about one hour to about ten days and can be isolated by filtration or other conventional methods.
Acids commonly employed to form acid addition salts are inorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, phosphoric acid, and the like, and acids commonly employed to form such salts are inorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, phosphoric acid, and the like, and organic acids, such as p-toluenesulfonic acid, methanesulfonic acid, oxalic acid, p-bromophenylsulfonic acid, carbonic acid, succinic acid, citric acid, benzoic acid, acetic acid and the like. Examples of such pharmaceutically acceptable salts thus are the sulfate, pyrosulfate, bisulfate, sulfite, bisulfite, phosphate, monohydrogenphosphate, dihydrogenphosphate, metaphosphate, pyrophosphate, chloride, bromide, iodide, acetate, propionate, decanoate, caprylate, acrylate, formate, isobutyrate, caproate, heptanoate, propiolate, oxalate, malonate, succinate, suberate, sebacate, fumarate, maleate, butyne-1,4-dioate, hexyne-1,6-dioate, benzoate, chlorobenzoate, methylbenzoate, dinitrobenzoate, hydroxybenzoate, methoxybenzoate, phthalate, sulfonate, xylenesulfonate, phenylacetate, phenylpropionate, phenylbutyrate, citrate, lactate, xcex2-hydroxybutyrate, glycollate, tartrate, methanesulfonate, propanesulfonate, naphthalene-1-sulfonate, naphthalene-2-sulfonate, mandelate and the like.
The term xe2x80x9cbase addition saltxe2x80x9d refers to a salt of a compound of formula I prepared by reaction of a compound of formula I with a mineral or organic base. For exemplification of pharmaceutical base addition salts see, e.g., Berge, S. M, Bighley, L. D., and Monkhouse, D. C., J. Pharm. Sci., 66:1, 1977. This invention also contemplates pharmaceutical base addition salts of compounds of formula I. The skilled artisan would appreciate that some compounds of formula I may be acidic in nature and accordingly react with any of a number of inorganic and organic bases to form pharmaceutical base addition salts. Examples of pharmaceutical base addition salts are the ammonium, lithium, potassium, sodium, calcium, magnesium, methylamino, diethylamino, ethylene diamino, cyclohexylamino, and ethanolamino salts, and the like of a compound of formula I.
While all of the compounds of the present invention are useful, certain of the compounds are particularly interesting and are preferred. The following listing sets out several groups of preferred compounds. It will be understood that each of the listings may be combined with other listings to create additional groups of preferred embodiments.
1) E is a bond;
2) E is xe2x80x94C(R4)(R4)xe2x80x94;
3) When E is xe2x80x94C(R4)(R4), R4 is hydrogen;
4) When E is xe2x80x94C(R4)(R4), R4 is methyl;
5) R1 and R2 are hydrogen;
6) R3 is C1-C6 alkyl;
7) R3 is optionally substituted C3-C8 cycloalkyl;
8) R3 is optionally substituted (C1-C4 alkyl) C3-C8 cycloalkyl;
9) R3 is optionally substituted (C1-C4 alkyl)-aryl;
10) R3 is optionally substituted aryl;
11) R3 is optionally substituted (C1-C4 alkyl)-heterocycle;
12) R3 is optionally substituted heterocycle, C1-C6 alkoxy,
13) R3 is optionally substituted Oxe2x80x94(C3-C8 cycloalkyl);
14) R3 is optionally substituted (C1-C4 alkoxy) C3-C8 cycloalkyl;
15) R3 is optionally substituted (C1-C4 alkoxy)-aryl;
16) R3 is optionally substituted O-aryl;
17) R3 is optionally substituted (C1-C4 alkoxy)-heterocycle;
18) R3 is optionally substituted O-heterocycle;
19) R5 is hydrogen;
20) R5 is methyl;
21) The compound is a pharmaceutical salt; and
22) The compound is the hydrochloride salt.
The compounds of the present invention can be prepared by a variety of procedures, some of which are illustrated in the Schemes below. The particular order of steps required to produce the compounds of formula I is dependent upon the particular compound being synthesized, the starting compound, and the relative lability of the substituted moieties.
Compounds of formula I may be prepared from compounds of formula II as illustrated in Scheme 1 below, wherein Y is C(O)R4 or xe2x80x94Exe2x80x94NR5C(O)R3, R1 and R2 are hydrogen, and E, R3, R4, and R5 are as described supra. 
Compounds of formula I may be prepared by combining a compound of formula II in a suitable solvent, preferably acetonitrile/water (5:1 ratio), and adding a suitable reducing agent, such as hexacarbonylmolybdenum.
The reactants are typically combined at a temperature from about 0xc2x0 C. to about 100xc2x0 C. The reactants are preferably combined at room temperature and the resulting solution is typically heated to reflux and mixed until the reaction is complete, as measured by the consumption of the substrate. The final product may be isolated and/or purified by standard techniques well known in the art.
Compounds of formula II may be prepared from compounds of formula III as illustrated in Scheme 2 below, wherein Y is C(O)R4 or xe2x80x94Exe2x80x94NR5C(O)R3. 
Compounds of formula II may be prepared by dissolving or suspending a compound of formula III in a suitable solvent, preferably dimethylformamide, and adding a suitable base, such as potassium methoxide, potassium tert-butoxide, potassium carbonate, sodium hexamethyldisilazane, or preferably potassium hexamethyldisilazane. The base is typically employed in an one to one ratio. However, as the skilled artisan would appreciate, a slight molar excess, usually in about a 1.1 to about a 3 fold molar excess relative to the compound of formula III, is acceptable.
The reactants are typically combined at a temperature from about 0xc2x0 C. to about 100xc2x0 C. The reactants are preferably combined at room temperature and the resulting solution is typically mixed for from about 5 minutes to about 18 hours, preferably from about 15 minutes to about 3 hours.
Any protecting groups remaining in the cyclized compound of formula I may be removed as taught in Greene to provide the compounds of formula II. Preferred choices of protecting groups and methods for their removal may be found in the Preparations and Examples sections below.
Compounds of formula II may be prepared from compounds of formula (i) as illustrated in Scheme 3 below where E, R3, R4, and R5 are as described supra. 
The compounds of formula (i) may be reductively aminated to form the compounds of formula II. Reductive aminations are well known transformations, see, e.g., Larock, xe2x80x9cComprehensive Organic Transformationsxe2x80x9d, pg. 421, VCH Publishers, New York, N.Y., 1989, hereafter referred to as xe2x80x9cLarockxe2x80x9d. 
Amines of formula (a) may be dissolved or suspended in a suitable solvent, optionally in the presence of a suitable base, preferably N-methyl morpholine or triethylamine, when the compound of formula III is an acid addition salt to convert the salt to its free amine form, and a compound of formula (i) is added. A Lewis acid catalyst, such as titanium(IV) isopropoxide, may optionally be employed. Once it is determined that the compound of formula (i) has been substantially consumed, the intermediate is typically reacted in situ with a suitable reducing agent to provide the compounds of formula II. The overall conversion may be performed at about 0xc2x0 C. to the boiling point of the mixture, but room temperature is a preferred reaction temperature. The formation of the compounds of formula II may take from 15 minutes to 24 hours as measure by the consumption of the compound of formula (i). Methanol is typically a preferred solvent.
Suitable reducing agents include, but are not limited to, hydrogen over palladium or platinum on carbon, borane or complexes of borane, e.g., borane-pyridine, borane-t-butylamine, and borane-dimethylamine complex; and borohydride reducing agents such as sodium borohydride or sodium cyanoborohydride. Sodium cyanoborohydride is a preferred reducing agent.
Compounds of formula (ii) and (iii) may be combined to prepared compounds of formula III according to Scheme 4, wherein Y is defined supra. 
Compounds of formula (ii) may be converted to the corresponding acid halide by methods well known to one skilled in the art. Compounds of formula III may be prepared by dissolving or suspending an acid halide of a compound of formula (ii) in a suitable solvent and adding a compound of formula (iii) in a suitable solvent. Triethylamine or dimethylformamide is a suitable solvent and is typically preferred for the compound of formula (ii). A 1:1 mixture of DMF and dichloromethane is a convenient solvent and is typically preferred for the amine of formula (iii). This amide forming reaction is also preferably run in the presence of 4-dimethylaminopyridine (DMAP).
The compound of formula (ii) is preferably employed in an equimolar amount, relative to the compound of formula (iii), but a slight excess (about a 0.05 to about 0.15 molar excess) is acceptable. DMAP is employed in a catalytic fashion. For example, about 5 molar percent to about 15 molar percent, relative to the compound of formula (iii), is typically employed. A 10 molar percent is usually preferred.
Compounds of formula (iii), wherein Y is defined supra, are well known in the art and to the extent not commercially available, are readily synthesized by standard procedures commonly employed in the art.
The synthesis of compounds of formula (ii) may be performed as described in Route 1 below. 
Compounds of formula XVI may be prepared by dissolving or suspending a compound of formula XV and a suitable base in a suitable solvent and adding a compound of formula XIV in a suitable solvent, dropwise. Toluene is a convenient solvent and is typically preferred. Triethylamine is the preferred base. The compound of formula XIV is typically and preferably employed in an equimolar amount, relative to the compound of formula XV, but a slight excess is acceptable.
The reactants are preferably combined at about 0xc2x0 C. and the resulting solution is typically warmed to room temperature and mixed for from about 18 hours to about 24 hours.
The compound of formula XVI may then be converted to the compound of formula XIII by dissolving or suspending a compound of formula XVI in a suitable acidic solvent and adding hydroxylamine hydrochloride. Glacial acetic acid is a convenient acidic solvent and is typically preferred. The ester group is then hydrolyzed to the corresponding carboxylic acid of formula (ii) through standard procedures commonly employed in the art, see for example, Larock, pgs 981-985.
The reactants are preferably combined at about room temperature then heated to reflux for from about 30 minutes to about 60 minutes. Preferably the reaction is heated to reflux from about 40 to 45 minutes.
Compounds of formula XIV and XV are known in the art and, to the extent not commercially available, are readily synthesized by standard procedures commonly employed in the art.
Compounds of formula XIX may be prepared in a manner similar to that described in the literature, for example, see Liu K, Shelton B R, Howe, R K, J. Org. Chem., 1980, 45, 3916-3918.
The pharmaceutical salts of the invention are typically formed by reacting a compound of formula I with an equimolar or excess amount of acid or base. The reactants are generally combined in a mutual solvent such as diethylether, tetrahydrofuran, methanol, ethanol, isopropanol, benzene, and the like for acid addition salts, or water, an alcohol or a chlorinated solvent such as dichloromethane for base addition salts. The salts normally precipitate out of solution within about one hour to about ten days and can be isolated by filtration or other conventional methods.
Acids commonly employed to form pharmaceutical acid addition salts are inorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, phosphoric acid, and the like, and organic acids such as p-toluenesulfonic, methanesulfonic acid, ethanesulfonic acid, oxalic acid, p-bromophenylsulfonic acid, carbonic acid, succinic acid, citric acid, tartaric acid, benzoic acid, acetic acid, and the like. Preferred pharmaceutical acid addition salts are those formed with mineral acids such as hydrochloric acid, hydrobromic acid, and sulfuric acid, and those formed with organic acids such as maleic acid, tartaric acid, and methanesulfonic acid.
Bases commonly employed to form pharmaceutical base addition salts are inorganic bases, such as ammonium or alkali or alkaline earth metal hydroxides, carbonates, bicarbonates, and the like. Such bases useful in preparing the salts of this invention thus include sodium hydroxide, potassium hydroxide, ammonium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, calcium hydroxide, calcium carbonate, and the like. The potassium and sodium salt forms are particularly preferred.
It should be recognized that the particular counterion forming a part of any salt of this invention is not of a critical nature, so long as the salt as a whole is pharmacologically acceptable and as long as the counterion does not contribute undesired qualities to the salt as a whole.
The optimal time for performing the reactions of the Schemes and the Route can be determined by monitoring the progress of the reaction via conventional chromatographic techniques. Furthermore, it is preferred to conduct the reactions of the invention under an inert atmosphere, such as, for example, argon, or, particularly, nitrogen. Choice of solvent is generally not critical so long as the solvent employed is inert to the ongoing reaction and sufficiently solubilizes the reactants to effect the desired reaction. The compounds are preferably isolated and purified before their use in subsequent reactions. Some compounds may crystallize out of the reaction solution during their formation and then collected by filtration, or the reaction solvent may be removed by extraction, evaporation, or decantation. The intermediates and final products of formula I may be further purified, if desired by common techniques such as recrystallization or chromatography over solid supports such as silica gel or alumina
The skilled artisan will appreciate that not all substituents are compatible with all reaction conditions. These compounds may be protected or modified at a convenient point in the synthesis by methods well known in the art.